Indonesian Journal of Electrical Engineering and Computer Science Vol. 25, No. 2, February 2022, pp. 1030~1037 ISSN: 2502-4752, DOI: 10.11591/ijeecs.v25.i2.pp1030-1037  1030 Journal homepage: http://ijeecs.iaescore.com Free space optical communication system for indoor applications based on printed circuit board design Alsharef Mohammad 1 , Mohammed S. Alzaidi 1 , Mahmoud M. A. Eid 1 , Vishal Sorathiya 2 , Sunil Lavadiya 2 , Shobhit K. Patel 3,4 , Ahmed Nabih Zaki Rashed 5 1 Department of Electrical Engineering, College of Engineering, Taif University, Taif, Saudi Arabia, 2 Department of Information and Communication Technology, Marwadi University, Rajkot, India 3 Department of Electronics and Communication Engineering, Marwadi University, Rajkot, India 4 Department of Computer Engineering, Marwadi University, Rajkot, India 5 Department of Electronics and Electrical Communications Engineering, Faculty of Electronic Engineering, Menoufia University, Al Minufiyah, Egypt Article Info ABSTRACT Article history: Received Aug 27, 2021 Revised Dec 1, 2021 Accepted Dec 9, 2021 This study clarified an overview of wired and wireless optical communication system block diagram with practical applications. Free- space optical (FSO) communication is a trending field that is rising so fast to replace electromagnetic waves in a communication, so we have presented a theoretical circuit as an example and modified it to fit and work in communication purposes, simulation is used and then practical work is done and printed circuit board (PCB) is designed. Light emitting diode (LED) have been used as transmitter and Photo Transistor as a receiver and variable resistance to change voltage sent to the LED that indicates the change in the transmitted signal. Keywords: Light-emitting diode Phototransistor Printed circuit board Variable resistance This is an open access article under the CC BY-SA license. Corresponding Author: Ahmed Nabih Zaki Rashed Department of Electronics and Electrical Communications Engineering Faculty of Electronic Engineering Menoufia University Al Minufiyah, Egypt E-mail: ahmed_733@yahoo.com 1. INTRODUCTION The bit error rate (BER) is optimized with four-wave mixing (FWM) optical wavelength division multiplexing systems. The main target of work is to achieve the highest quality of services by reducing the BER effects. They have outlined the different optical multiplexing schemes such as orthogonal frequency division, wavelength division multiplexing (WDM), and dense wavelength division multiplexing (DWDM) schemes [1]-[8]. The applications of FWM is presented in order to achieve a minimum BER. The link budget and receiver sensitivity design are studied for different optical fiber lengths and signal attenuation to show the maximum Q-factor value and corresponding minimum BER values. Mathematical analysis, computer, and simulation programs are performed to estimate the optimum fiber optic cable length that achieves max. Q-factor value and min. BER values in the presence of non return to zero code modulation formats [9]-[18]. They have presented a competing survey about the BER optimization in optical fiber communication systems [19]-[25]. The BER is estimated mathematically in the presence of nonlinear distortion interaction and amplified spontaneous emission effect [26]-[30]. Return to zero, non return to zero signal generators are coupled with optical modulators for 8-bit sequence of (10101100) at power variations values from 15 dBm to 20 dBm to test the min BER values. Different optimization methods are employed in optical WDM systems using